The present invention relates generally to the field of hydraulic circuits within automatic transmission systems for land vehicles and, more particularly, to a Torque Converter Clutch Regulator Valve Assembly (hereinafter xe2x80x9cTCCRV Assemblyxe2x80x9d) that directs fluid pressure to apply and/or release the torque converter clutch within the torque converter of the transmission.
The Chrysler 41TE and 42LE transmissions (hereinafter the xe2x80x9cChrysler transmissionsxe2x80x9d) are equipped with mechanisms to xe2x80x9clockupxe2x80x9d their torque converters under certain operating conditions. The purpose of the lockup converter is to provide for direct drive when the vehicle is cruising at higher speeds. Since there is always some slippage in the fluid coupling of a torque converter, some power is lost and fuel economy suffers. By providing a direct mechanical coupling through the transmission at high engine speeds, the lockup converter improves fuel economy.
This is accomplished by an electronic/hydraulic torque converter clutch system, which utilizes a lockup piston within the torque converter housing. The lockup piston has friction material on its forward surface. When the vehicle is at cruising speed and lockup is desired, an electric solenoid is energized that strokes the Torque Converter Clutch Switch Valve in the valve body. This opens a port to allow fluid pressure to act upon the lockup piston, which is forced against a machined surface on the converter cover. Thus, the lockup piston and the converter cover are locked together and act as a single unit similar to a manual transmission clutch. Because the lockup piston is mechanically coupled to the transmission input shaft, a direct mechanical link through the torque converter to the drive wheels is established.
When lockup is no longer required, a port opens that allows the pressurized fluid to exhaust. The lockup piston then moves away from the torque converter housing reestablishing the fluid coupling. Lockup in electronic torque converter clutch systems is controlled by the vehicle""s computer module. When the computer module senses the engine is warm and the vehicle is traveling at a steady speed of about 40 miles per hour, lockup is initiated. When speed falls below about 40 miles per hour, the brakes are applied, or a lower gear is selected, apply pressure is exhausted to end lockup.
A common service complaint in automotive vehicles employing the aforementioned Chrysler transmissions is the lack of hydraulic control over the torque converter clutch. The torque converter clutch requires both hydraulic flow and pressure matched to engine torque load to prevent slippage, overheating, shudder, deflection and/or breakage of the lockup piston. The original equipment manufacture (hereinafter xe2x80x9cOEMxe2x80x9d) hydraulic control does not adequately limit fluid pressure or control flow to the torque converter clutch piston. Normal operating pressure affecting the torque converter clutch is controlled by the line pressure regulator valve, which feeds the torque converter clutch. During the time the torque converter clutch is not applied, a derivative of line pressure (i.e. cooler/converter pressure) is feeding automatic transmission fluid (hereinafter xe2x80x9cATFxe2x80x9d) to the release circuit of the converter. Such cooler/converter pressure is generally 50% or less than line pressure.
The inefficiency of the OEM design is particularly evident when the computer module controls torque converter clutch apply using line pressure. The concern is that line pressure can rapidly increase up to 140 pounds per square inch (psi) or more, which causes internal distortion of the torque converter clutch piston.
There are known prior art patents that are available in the field and their discussion follows. One example is U.S. Pat. No. 4,271,939 to Iwanga et al., which discloses a hydraulic control system for a torque converter for ensuring release of the lock-up condition of the torque converter. This is accomplished by providing a flow restrictor in the hydraulic working fluid supply passage for the torque converter to make the flow resistance of the passage equal to or larger than the flow resistance of the hydraulic working fluid supply passage for the lock-up control chamber. In this control system a first or feed passageway communicates with a source of pressurized fluid and with a torque converter chamber, a second or discharge passageway communicates with the torque converter chamber and a third passageway communicates with a lock-up control or clutch chamber of the lockup clutch. A lockup control valve communicates with the same source of pressurized fluid and with the third passageway. The first passageway is provided with the flow restrictor. With the provision of the flow restrictor, the disengagement of the lockup clutch will be assured upon pressurization of the third passageway.
Another example is U.S. Pat. No. 4,618,036 to Ideta, which discloses a hydraulic control system for the lockup clutch of a torque converter wherein release of a lockup clutch is ensured even when the discharge flow rate of the pump is low. This control system comprises a pump driven by an engine to discharge fluid, a torque converter having a lockup clutch with a lockup clutch piston movable to a clutch released position when fluid pressure within a lockup release chamber is higher than fluid pressure within a working chamber in the torque converter cavity, a line pressure regulator valve and an orifice, which provides a restricted flow communication between the torque converter and the pump even when line pressure generated by the line pressure regulator valve is lower than a predetermined value. The Ideta (""036) patent utilizes cutouts 20 formed on the land 32d of the first spool 32 (FIG. 1) on the line pressure regulator valve to permit a sufficient flow of hydraulic fluid via oil conduit 62 to torque converter 10 at low speed operation to ensure the release of the lockup clutch.
The present invention provides advantages over the prior art and is disclosed hereinafter in further detail.
Accordingly, the present invention is a replacement Torque Converter Clutch Regulator Valve (TCCRV) Assembly for an automatic transmission including an internal pressure relief valve that regulates torque converter clutch apply circuit pressure to the lockup piston in the range of 90-100 psi in comparison to the OEM line pressure of 130 to 140 psi, which prevents deflection and/or breakage of the lockup piston. In addition, the present TCCRV Assembly includes a modified Switch Valve having a fluid restricting baffle formed thereon that delays fluid pressure build up in the clutch apply circuit and prevents the initial spike in clutch apply circuit pressure to the lockup piston within the torque converter clutch providing improved control of the clutch apply and release circuits.
Thus, there has been outlined rather broadly the important features of the present invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto.
Those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods, and systems for carrying out the purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.